The present invention relates to a method and system for desulfurizing gasoline, diesel fuel or like hydrocarbon fuels so as to reduce the sulfur content of the fuel and render the fuel suitable for use in a fuel cell power plant. More particularly, the method and system of this invention include the use of a sulfur scrubber which utilizes a modified version of the Claus reaction, and also include a technique for regenerating the sulfur scrubber bed by removing sulfur from the scrubber bed.
Gasoline, diesel fuel, and like hydrocarbon fuels can be useful as a stock fuel for powering a fuel cell power plant if the sulfur compounds in such stock fuels are removed from the fuel stream prior to its entry into the fuel cell stack section of the power plant. The sulfur compounds are undesirable since they are known to poison catalysts used in the fuel fuel processor and cell stack sections of the power plant. These fuels and other sulfur-containing fuels can be reformed to produce a hydrogen-rich gas stream. After the fuels have been reformed, they are typically passed through a sulfur scrubber bed which converts the hydrogen sulfide in the reformed fuel stream to sulfur and water, or in the case of a metal oxide scrubber such as zinc oxide, to a metal sulfide, such as zinc sulfide, and water. The scrubbing reaction causes sulfur to deposit on the scrubber reagent and after a time, the scrubbing reagent will be so sated with sulfur as to be incapable of removing sufficient sulfur from the reformer exhaust stream. When this condition comes about, the scrubber bed will be removed from the power plant, discarded, and replaced with a fresh scrubber bed. Sulfur content detectors are used to monitor the sulfur content of the effluent from the sulfur scrubber bed and to indicate when the scrubber bed should be replaced.
It would be highly desirable to provide a fuel cell power plant which includes a sulfur scrubber rejuvenating system which utilizes a by-product of the power plant to remove sulfur from the scrubber, so that sulfur-containing fuels can be processed for use in providing a hydrogen-rich fuel which can be used in the fuel cell stack power section of the power plant.
This invention relates to a system and method for processing a reformed sulfur-containing fuel such as gasoline, diesel fuel, or some other sulfur-containing hydrocarbon fuel stream over an extended period of time, which system and method are operative to remove substantially all of the sulfur present in the reformed fuel stream, which sulfur is present in the form of hydrogen sulfide. A sulfur-scrubbing bed is included in the system, which bed converts the hydrogen sulfide in the reformed fuel stream, to which a small quantity of oxygen has been added, to elemental sulfur and water by means of the Claus reaction, the elemental sulfur being removed from the gas stream and being deposited on the scrubbing bed.